Gear testers



1956 E. TURNER 2,731,728

GEAR TESTERS Filed April 9, 1954 2 Sheets-Sheet 1 MASTER GEAR INVENTOR. LLOYD E. TURNER ATTYS.

L E. TURNER GEAR TESTERS Jan. 24, 1956 2 Sheets-Sheet 2 Filed April 9, 1954 INVENTOR. LLOYD E. Tunmm Fla? United States Patent- The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

This invention relates to Gear Testers, and is particularly directed to mechanisms for comparing the concentricity of the various tooth circles and tooth contours of an unknown gear with a standard 'or'maste'rgea rn The transmission of motion'from one shaft to another always means transmission of power from one point to another even though the amount of power may vary from industrial values to near-zero values. Where, however, the informational content of shaft rotation to be transmitted through gear trains is of paramount importance, the order of tolerances in wheel and "tooth dimensions are entirely difierent from the tolerances usually thought of in the manufacture of power-gears. The tolerances required for testing power-gears has led to techniques unsuited for testing information-gears. equipment for testing automobile differential gears for uniformity comprises arbors for'receiving a' master gear and a gear to be tested, means for meshing the gears under considerable pressure, and means for indicating the movement between arbor centers as the gears are driven. The fact that the carriage for the movable arbor may travel in tight or sticky ways is of no importance sures and power applied during testing are relatively'high. Such a technique is unsuited for testing for the precision contemplated here. For testinggears for informationtype gear trains, it has been found that'the master gear;

the gear to be tested under precisely controlled yieldable pressure. The meshing pressure must not only be reproducible from gear to gear, but must be uniform throughout the test for each gear."

The principal object of this invention is an improved gear tester.

A more specific object of this invention is a devicefor' running a gear to be tested enmeshed with a master gear, with means for accurately predetermining the enmeshing pressure.

A still more specific object of this invention is a device for running a gear to be tested enmeshed with a master gear, with means for maintaining the enmeshing pressure uniform throughout the run.

A still further object of this invention is a device for running a gear to be tested enmeshed with a master gear,

with means for reliably indicating the variations in distance between the centers of the two gears.

The objects of this invention are attained in a machine having a bed with elongated ways. A first arbor is centered over and carried by the ways, while a second arbor parallel to the first arbor is mounted on a free swinging arm, the center line of the journal for the arm being displaced laterally from the ways and being parallel to the two arbors so that one arbor is free to move in an arcuate path toward and away from the other arbor. The master gear and the gear to be tested are, respectively, placed on the two arbors and a leaf spring extending from th s one end of the arm is flexed by an adjustable stopto rggi late the enmeshing pressure of the two gears. A pl er type displacement meter is placed in operating c'onta't with the swinging end of the arm to measure movement between the two gear centers. .1 In

For example,

because the pres-- Other objects and features of this invention will occur to those skilled in the art when reference is made to the preferred embodiments described in the following specification and illustrated in in which: 1

Figure 1 is a of the gear tester of this invention,

Figure 2 is a partial sectional elevational view of Figure 1,

Figure 3 is a view of the gear tester of this invention taken along line 3-3 of Figure l,

Figure 4 is a sectional view of the gear tester taken along line 4-4 of Figure 1,

Figure 5 is a detailed view of a worm gear holder attachment for the machine of Figure 1, and

Figures 6 and 7 are elevational views of an attachment for adapting a helical gear to the machine of Figure 1.

Referring first to Figures 1 and 3, vertical upstanding arbors 1 and 2 are parallel'and extend upwardly from support hubs 3 and 4, respectively. The polished upper surfaces. of the hubs from which the arbors extend are exact parallelism. On

the accompanying drawings reversed on the arbors. Each has a center hole accurately machined in diameter to receive its arbor without play, and each has a right angle machined hub face to ride evenly. on the upper surface of the support hubs 3 and 4. The master gear and gear to be tested are brought to mesh with a light yieldable pressure determined by means to be hereinafter described. A position indicator 7 with a plunger 8 is brought to bear upon the base of one support hub to indicate the slightest movement of that hub with respect to the other. Since the other hub support 4 is stationary, the dial of the indicator will show variations in distance between arbor centers.

To insure that the enmeshing pressure between the two gears will not vary and hence cause false indications of variable pitch diameter, the support hub 3 is mounted according to this invention upon a support which can move with near-zero friction. Support hub 3 and its mounting with means for accurately determining enmeshing pressure will be described in detail below.

The operating parts of this gear tester are mounted on the bed 10 having a straighter accurately machined longitudinal T-slot or way 11. The overhang flanges of way 11 receive a draw bolt 12 to adjustably clamp the arbor stock 13 in any desired longitudinal position along the way. A stud 14 fixes the support hub 4 to the stock. At the opposite end of the way is a second draw bolt 15 and bracket 16 for adjustably supporting the dial indicator 7. A plane including the center line of the way, the tip of the'plunger 8 and the center lines of the arbors 1 and 2 is carefully maintained so that motion between the arbor centers is directly readable without distortion on the dial of the indicator 7. Indicator '7 is preferably of the type which can translate thrust of the plunger 8 into rotary motion for the indicator hand, as by a rack and pinion 17,

with or without motion amplification. Commercial indi-' plan view of the preferred embodiment 19a. toseat up on themachined top of the bed, the seating pressure to be made by the threaded nut 20. Widely spaced ball bearing 21 and 22':;on the king pin carries the hub.23 and an:arrrr:24-:fabricated integrallywithdhehub.

Atthe outer or;free-.- end-ofttheqarm is mounted. the.

support hub :3and=its arbor-1. The .supporthub is-removably tightened-implace by aknurled: handiwheel ZSJand:

threaded stud 26 so that arbors of difierent sizes may be;

used. The bearings are; preferably: adjustable so; that all side and end play may be removed andhence sozthat the upstanding orientation: of the :arbon 1 .will not .be. disturbed by wear as the arm swings toward or away from arbor-2. The: length;of :the. arm 24=and the. placement of the hinge pin are so. chosen ,that .whensthearmgz i-sis.

are threadedlin the=bracketzon either side-.otcthe lugxto.

preset thelimits of traveloffthelug'and' arml4a. Arnide position of the lugis. fixed by the-thumb'screw31. With:

suchlimited motion, as insured by. the.;set. screws; thev arcuate travel of arbor lidoes not practicallydeviatefrom1 straight line travel in theplane mentioned;

To adjust the enmeshing pressure.between the: master gear and the. gear to betested the leaf'spring'32 is fixedly attached to thearm 2.4.and issextended"substantially:in.

alignment with-the arm 24. Thenouterend of .theileaf. spring may be flexed out: of. said alignment: to apply enmeshing pressure to the. gears. Conveniently; the outer end of the leaf spring-is pressed 'byrollers 33 carried -on a. stub shaft 34 which isin turn attached'to .the calibrated plunger 35. Plunger 35 is slidable lengthwise to the ways and may be fixed-in any desired longitudinal position between thumb screw- 36. Indicia onthe plunger is marked to indicate the deflectionpressure in ounces applied at the center of the gear being checked;

All plane surfaces are accurately-machined, ground, and

polished and the arb'ors are preferably hardened after machining.

To set-up the gear tester of this invention preparatory to comparing two gears, the leaf Spring is flexed an amount to obtain the pressure required for'testing these particular gears. This pressure is'preferably approximately equal to the pressure prescribed by the-American Gear Mann facturers Association. For example, a gear .100 wide and with a diametral pitch of 20 to 30 should be-mesh'ed' with the standard gear under a pressure of 28 ounces, and a-gear with a di'ametral pitch of '50to 60 would'require a pressure of 16 ounces. Diametral pitch is the ratio of the number of'teeth to the number of 'inches of pitch diameter. Then, the thumb screw 31 is adjusted .to' move the stud 28 midway between the set screws wand-3C. The arm 24 then strands perpendicular to the ways 11, and the arbor is in the vertical plane through arbor 4. Next, draw bolt 12 is loosened and the stock 13'is shifted by tapping until the distance between center of the arbors is'the exact spacing required for the two gears; This'spacing-between arbors may be measured by gage blocks laid between. the arbors,: whereupon the draw bolt 12 is tightened. Next the gears are'lowered'on their respective arbors; and the thumb screw 31 is retracted.v Finally, the

gearon the stationary arbor 4 is rotated-slowly by hand and the behavior of the indicator needle noted; If theneedle stands stationary throughout arcvolutionof the gear under test, the pitch circle is known to be concentric with-the center:ot the*-gear;. 'If the =needl'e=-defleets-from" itszeroor startingposition asindividnal'teethare-brought into mesh, the. thickness of'the-tooth'willjbe-found tube too thick or too thin:

The amount of leaf spring pressure applied to any particular gear to be tested will depend of course upon the width of the gear teeth. As the arbor 1 moves in response to irregularities in individnal-teethor in response to eccentricities of the pitch circleof'the gear, the indicator will respond. Because of the uniform pressure applied by the: springs andthe' frictionless supp ort.of the arbor 1 the wedging action between any pair of enmeshing teeth will be uniform.

Referring to Figure 5;.where a worm gear must be matched with a worm, the worm' 40" may be mounted upon a mandrellli or cutinan integral one-piece'round shaft whichis held-betweencenters .42 and143 mounted ina Y.-bracket=.44.. The. Y-,-bracket and itsbase portion issodimensioned-and finished that thebracket may replace the support hub 4 of. Figured. The-position of the worm is then in. a..horizontaltplanezparallelto thezbed andpasses through. the center of.the. Worrn gear, on arbor .1, to. which-.the .rnastenworm is .to. be-rnatched.

Where .helical.-gears- -mustbe..tested, .the arbor carrying;

the spur. masters gear. mustbe .rotated, from the upstanding position of Figure, 1'. throughatan angle proportional to,the. helix ofthegear; ThearborA,,inFigure-7, is car-. riedupprra-bracket Shattached .toaa yoke 51 pivoted on a, bolt 52; with .a.- center line-through. the -median point ofthe enmeshinggpars. Coaxial withthe bolt 52 on thepivotedyokemay, if desired,; be placed a dividing head 53, with graduation-marks in.-degr,ees. and minutes on .the head toindicate .the helical pitch-angle. The technique-of placingthemastergear. andtcst gear on the arbors, applying the-leaf .spring, pressure, and reading deflections on:indicator 7- are the sameas with the spur.

gear apparatusof Figure 1.

A worm drive 54 withihand wheel 55:may be employed for. moving the ,yoke. and ttheearbor; 4' supported thereon. A bracket 57 is-tprovidedvfor; locking the. yoke in any position: tremovablmv dowel pinv 56:may be. used if desired through aligned :holes .in the stationaryheadstock and theapivoteddividingheaddo indexthe head to its zero position. Y

The vswingingfifictionlessearrnand the leafcspringon the arm of-this invention :insures Matchmaker-accuracy in testing gears.-.

What is claimed is:

A gear. tester for;comparingr;a:first-gear witha second gear, said tester comprising. a .bed: witl1:ways, a. first arbor adapted to receive onerofisaidzzgears.centerednver and carried by said ways, an elongated bearingscarriedi by said bedand--displacedilaterally fromsaid ways, .an

arm pivotlymounted atone .endron saidrbearing; a second arbor adapted to TGCGiYEithC :other :ofsaid gears mounted.

on the other end of said arm, the second arboriposition being,-.;substantia1ly.-' centered over said; ways; then-center lines of saidfarbiorsgand zsaidibearing :being preciselytpar? i allel a leaf .springmattacheditoathe;arbor-end; of said arm and extending beyond the endsof the arm" to aipointlat erally w of said Will/S1 opposites. saidi bearing,-.. a; calibrated plunger slidably mounted..to. said: ways, a stub'shaft attached to said calibrated'plunger, and. at least one roller rotatably mountedzonrsaidstnb shafL-andiengaging saidleaf. spring whereby; difierenhlongitudinal positions of said.;calibrated: plunger. change:.the=. degree: of flexure of said: leaf spring;

Referencesfiited tin-the file of this, patent UNITED STATES PATENTS 

